1. Field of the Invention
This invention refers to a method and a device for providing spot heating of a body, particularly for carrying out brazing of hard solder gold alloys.
2. Description of the Prior Art
In dental science the molded components of dental gold alloy bridges are united by hard soldering or brazing. At the present time this brazing is carried out with a gas torch flame, for example a flame generated by bottled gas with compressed air or by acetylene and oxygen. However, when the quality of hard solderings performed in this manner is investigated it turns out that defects occur quite often. Thus, in an investigation it has been found that in X-ray detection, wherein defects greater than 0.2 millimeters were detected, defects could be observed in 34% of the examined material.
Furthermore, the fracture surfaces of fractured dental bridges have been studied in a metallographic study. In all of the investigated cases defects were located, such as porosities and inclusions, and at the same time striation patterns could be observed which originated in said defects. These striation patterns show that the fracture is a result of fatigue.
From the above-mentioned investigations the conclusion can be drawn that defects in a brazing of a gold solder alloy can be considered to have great importance for the strength of the dental soldering. If the size and number of defects can be reduced it is possible to expect that a dental gold construction having extended duration may be attained.
Other investigations have shown that the solubility of gas in dental gold alloys can increase in consequence of the use of gas torch flame. This particularly occurs with gold alloys including palladium.
With the purpose of achieving better solderings efforts have been made with furnace soldering, wherein however the results have not been particularly successful because it is difficult to see when the hard solder melts.